This invention relates to rotary mechanisms and more particularly to rotary combustion engines of the type disclosed in U.S. Pat. No. 2,988,065 issued on June 13, 1961 to Wankel et al. Although the invention is herein described in connection with a rotary combustion engine, it will be clear that the invention is equally applicable to similar rotary mechanisms designed for use as rotary compressors or rotary expansion engines.
In such a rotary engine, the engine shaft has a cylindrical eccentric portion on which a rotor member is journaled. The shaft eccentric and its rotor member are received within the cavity of the engine housing. The engine housing cavity has a multi-lobe peripheral surface which, particularly in the case of a combustion engine, preferably is substantially an epitrochoid and the rotor member has a generally polygonal peripheral surface with a plurality of circumferentially-spaced apex portions. These apex portions have sealing cooperation with the housing multi-lobe peripheral surface to form a plurality of working chambers between the housing and rotor member. The engine shaft is provided with counterweights placed 180.degree. from the shaft eccentric to dynamically balance the shaft eccentric and the rotor member mounted on the shaft eccentric. The aforementioned Wankel et al patent and U.S. Pat. No. 3,891,357 granted June 24, 1975 to Davis et al and U.S. Pat. No. 3,077,867 granted Feb. 19, 1963 to Froede all show rotary engines with such counterweights.
It has been found, however, that when such a rotary engine is operated at high speeds, for example, over 6,000 rpm, that its housing is subject to excessive vibration.